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Re: [GHC] #1831: reify never provides the declaration of variables
by GHC 01 Mar '18

01 Mar '18

#1831: reify never provides the declaration of variables -------------------------------------+------------------------------------- Reporter: guest | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Template Haskell | Version: 6.8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by parsonsmatt): I'd like to register interest in having this available :) My specific use case is walking the AST from a given point to capture uses of `throw`, `throwM`, `throwIO`, etc. and try to get a list of possible exception types that might arise from a given function. eg: {{{ openFile' :: FilePath -> IO (Either IOException String) openFile' f = [catch|openFile f|] }}} It seems like this would be useful for other sorts of static analysis, as well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1831#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14856: GHC API: Linker failure on loading target multiple times
by GHC 01 Mar '18

01 Mar '18

#14856: GHC API: Linker failure on loading target multiple times ----------------------------------------+--------------------------- Reporter: fizzixnerd | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 8.2.2 Keywords: GHC API Linker | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------- Minimum Working Example: https://github.com/Fizzixnerd/ghc-bug `stack exec -- ghc --version` >The Glorious Glasgow Haskell Compilation System, version 8.2.2 `uname --all` >Linux <REDACTED> 4.14.0-3-amd64 #1 SMP Debian 4.14.13-1 (2018-01-14) x86_64 GNU/Linux Description: Loading a dynamic module more than once causes a linker failure with the following message: ''' /usr/bin/ld.gold: error: cannot find -lghc_2 collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) *** Exception: ExitFailure 1 ''' `-lghc_2' sometimes is `-lghc_5' or other numbers. Steps to Reproduce: 1) Clone above repo. 2) `stack build` 3) `stack exec mwe-exe` The repo code will use the GHC API to load a string from the file contained in scripts/ named `val'. There are three functions defined in src/Lib.hs. `anotherFunc' should behave normally. `someFunc' should display the bad behavior. Notes: - When using `intero`: intero must be restarted if this bug is encountered at the prompt, or else you will keep getting it over and over again. - I could not figure out how to load it up without using the `-dynamic' flag, but that should probably be checked out too. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14856> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14871: With process substitiution, ghc didn't read filedescriptor.
by GHC 28 Feb '18

28 Feb '18

#14871: With process substitiution, ghc didn't read filedescriptor. -------------------------------------+------------------------------------- Reporter: octaltree | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I ran ghc with process substitution as filename but ghc couldn't read the filedescriptor. I ran this script with bash and zsh, then I got the error. {{{#!sh #!/bin/sh H=''' main = putStrLn "Hello, World! ''' P=''' print("Hello, World!") ''' R=''' puts "Hello, World!" ''' stack ghc -- --version bash --version zsh --version cat --version python --version ruby --version echo '-----------------------' cat <(echo -n "$H") echo '-----------------------' stack ghc <(echo -n "$H") echo '-----------------------' python <(echo -n "$P") ruby <(echo -n "$R") }}} {{{ The Glorious Glasgow Haskell Compilation System, version 8.2.2 GNU bash, バージョン 4.4.19(1)-release (x86_64-unknown-linux-gnu) Copyright (C) 2016 Free Software Foundation, Inc. ライセンス GPLv3+: GNU GPL バージョン 3 またはそれ以降 <http://gnu.org/licenses/gpl.html> This is free software; you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. zsh 5.4.2 (x86_64-unknown-linux-gnu) cat (GNU coreutils) 8.29 Copyright (C) 2017 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. 作者 Torbjorn Granlund および Richard M. Stallman。 Python 3.6.4 ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux] ----------------------- main = putStrLn "Hello, World! ----------------------- target ‘/dev/fd/63’ is not a module name or a source file ----------------------- Hello, World! /dev/fd/63: No such file or directory @ realpath_rec - /proc/4024/fd/pipe:[1855404] (Errno::ENOENT) }}} I already reported to ruby. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14871> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14867: make targets for documentation not working
by GHC 28 Feb '18

28 Feb '18

#14867: make targets for documentation not working -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Documentation | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- None of the documentation targets mentioned in the Wiki work: https://ghc.haskell.org/trac/ghc/wiki/Building/StandardTargets#Documentatio… As far as I can see there's no mention of how to build documentation in the entire wiki. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14867> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14870: Runtime performance regression in 8.4
by GHC 28 Feb '18

28 Feb '18

#14870: Runtime performance regression in 8.4 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- varosi [[https://mail.haskell.org/pipermail/glasgow-haskell- users/2018-February/026701.html|reports]] that the code for his project is slower in 8.4.1 than 8.2.2: > Yesterday I successfully compiled it with GHC 8.4.1-rc1. I got compiled it > with 8.2.2 and 8.0.2 as well and ran tests for about a minute each on my > Intel Core i7 machine on Windows 10 x64. > > I got this results: > > GHC 8.4.1-rc1 > Average time: 61.87s > > GHC 8.2.2 > Average time: 60.09s > > GHC 8.0.2 > Average time: 67.07s > We should look into why. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14870> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14866: GHC 8.4.1 rc1 segfaults when compiling the influxdb package
by GHC 27 Feb '18

27 Feb '18

#14866: GHC 8.4.1 rc1 segfaults when compiling the influxdb package -------------------------------------+------------------------------------- Reporter: fumieval | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1-alpha3 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I tried to build influxdb-1.2.2.3 with GHC 8.4.1 rc1 built with DYNAMIC_GHC_PROGRAMS=NO. Then I got {{{ [ 8 of 10] Compiling Database.InfluxDB.Query ( src/Database/InfluxDB/Query.hs, /home/fumieval/hs/influxdb-haskell/dist- newstyle/build/x86_64-linux/ghc-8.4.0.20180224/influxdb-1.2.2.3/build/Database/InfluxDB/Query.p_o ) cabal: Failed to build influxdb-1.2.2.3. The build process segfaulted (i.e. SIGSEGV). }}} It seems to be related to Template Haskell, as it doesn't happen if I remove `makeLensesWith` in `Query.hs`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14866> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14196: Replace ArrayArray# with either UnliftedArray# or Array#
by GHC 27 Feb '18

27 Feb '18

#14196: Replace ArrayArray# with either UnliftedArray# or Array# -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple LevityPolymorphism | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Just to be clear, there currently is nothing named `UnliftedArray#`. I would like to propose that such a thing possibly be added, with the long- term goal of deprecating and removing `ArrayArray#`. The interface for it would look like this: {{{#!hs data UnliftedArray# (a :: TYPE 'UnliftedRep) data MutableUnliftedArray# s (a :: TYPE 'UnliftedRep) indexUnliftedArray# :: forall (a :: TYPE 'UnliftedRep). UnliftedArray# a -> Int# -> a writeUnliftedArray# :: forall (a :: TYPE 'UnliftedRep). MutableUnliftedArray# s a -> Int# -> a -> State# s -> State# s readUnliftedArray# :: forall (a :: TYPE 'UnliftedRep). MutableUnliftedArray# s a -> Int# -> State# s -> (# State# s, a #) unsafeFreezeUnliftedArray# :: forall (a :: TYPE 'UnliftedRep). MutableUnliftedArray# s a -> State# s -> (#State# s, UnliftedArray# a#) newUnliftedArray# :: forall (a :: TYPE 'UnliftedRep). Int# -> a -> State# s -> (# State# s, MutableUnliftedArray# s a #) }}} You would also have a few other things like `sameMutableUnliftedArray#`, `sizeofMutableArray#`, `unsafeThawUnliftedArray#`, `copyUnliftedArray#`, etc. The main difficulty that I see in doing this is that I'm not sure if you can tell a primop that it takes a polymorphic argument whose kind is something other than `TYPE LiftedRep`. The bodies of all of the functions I listed above could simply be copied from the `ArrayArray#` functions. There are a few alternatives I've heard discussed. One is to make `Array#` accepted both boxed or unboxed types. There is a brief discussion of this in the UnliftedDataTypes proposal [#point0 (0)]. Indeed, it appears that some have managed to smuggle unlifted data into `Array#` already, with the caveats one would expect [#point1 (1)]. This interface would look like: {{{#!hs data Array# (a :: TYPE k) data MutableArray# s (a :: TYPE k) indexArray# :: Array# a -> Int -> a -- same as before indexUnliftedArray# :: forall (a :: TYPE UnliftedRep). Array# a -> Int -> a }}} So instead of having `Array#` and `UnliftedArray#` as separate data types, we could have `Array#` handle both cases, but we would need to make a duplicate of every function that operates on `Array#`. This follows all of the appropriate rules for when levity polymorphism is allowed, and it should be backwards-compatible with the previous non-levity-polymorphic definition of `Array#`. I'm not sure how many things in the GHC runtime assume that the values inside an array are lifted, so this might cause a bunch of problems. If it is possible, this approach would be kind of neat because then `SmallArray#` could be similarly adapted. Anyway, I just wanted to get this out there. I would be happy to try implementing the first proposal (involving `UnliftedArray#`) at some point in the next six months. Any feedback on the idea would be appreciated. Also, any comments on how appropriate this is for someone new to contributing to GHC would be appreciated as well. Thanks. * [=#point0 (0)] https://ghc.haskell.org/trac/ghc/wiki/UnliftedDataTypes#Parametricity * [=#point0 (1)] https://www.reddit.com/r/haskell/comments/6v9rmg/an_unified_array_interface… -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14196> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7503: Bug with PolyKinds, type synonyms & GADTs
by GHC 27 Feb '18

27 Feb '18

#7503: Bug with PolyKinds, type synonyms & GADTs -------------------------------------+------------------------------------- Reporter: Ashley Yakeley | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.6.1 checker) | Keywords: GADTs, Resolution: | TypeInType Operating System: Linux | Architecture: x86_64 Type of failure: GHC rejects | (amd64) valid program | Test Case: Blocked By: | Blocking: Related Tickets: #14451 | Differential Rev(s): Wiki Page: | https://ghc.haskell.org/trac/ghc/wiki/GhcKinds/KindInference| -------------------------------------+------------------------------------- Changes (by kcsongor): * wikipage: => https://ghc.haskell.org/trac/ghc/wiki/GhcKinds/KindInference -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7503#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #855: Improvements to SpecConstr
by GHC 27 Feb '18

27 Feb '18

#855: Improvements to SpecConstr -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: task | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.4.2 Resolution: | Keywords: SpecConstr Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: N/A Blocked By: | Blocking: 915 Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by sgraf): Long story short, I had success with the following [https://github.com/sgraf812/ghc/compare/master...sgraf812:stream-fusion diff]. Currently, it optimizes `ex1` to this code: {{{ -- RHS size: {terms: 39, types: 21, coercions: 0, joins: 3/3} Main.$wex1 [InlPrag=NOINLINE] :: GHC.Prim.Int# -> GHC.Prim.Int# [GblId, Arity=1, Caf=NoCafRefs, Str=<S,U>, Unf=OtherCon []] Main.$wex1 = \ (ww_s4pl :: GHC.Prim.Int#) -> joinrec { $s$wgo_s4rk :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# [LclId[JoinId(3)], Arity=3, Str=<L,A><S,U><S,U>] $s$wgo_s4rk _ [Occ=Dead] (sc1_s4ri :: GHC.Prim.Int#) (sc2_s4rh :: GHC.Prim.Int#) = jump $s$wgo2_s4rc sc1_s4ri sc2_s4rh; $s$wgo1_s4rg :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# [LclId[JoinId(3)], Arity=3, Str=<S,U><S,U><S,U>] $s$wgo1_s4rg (sc_s4rf :: GHC.Prim.Int#) (sc1_s4re :: GHC.Prim.Int#) (sc2_s4rd :: GHC.Prim.Int#) = jump $s$wgo_s4rk sc_s4rf sc1_s4re (GHC.Prim.+# sc2_s4rd sc_s4rf); $s$wgo2_s4rc [Occ=LoopBreaker] :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# [LclId[JoinId(2)], Arity=2, Str=<S,U><S,U>, Unf=OtherCon []] $s$wgo2_s4rc (sc_s4rb :: GHC.Prim.Int#) (sc1_s4ra :: GHC.Prim.Int#) = case GHC.Prim.<# sc_s4rb ww_s4pl of { __DEFAULT -> sc1_s4ra; 1# -> jump $s$wgo1_s4rg (GHC.Prim.*# sc_s4rb sc_s4rb) (GHC.Prim.+# sc_s4rb 1#) sc1_s4ra }; } in jump $s$wgo2_s4rc 1# 0# }}} Which is just a stone throw (or rather an inlining pass) away from the `goal`! For the examples `ex{2,3}` with increasing nesting level, things don't look so bright yet. Also I got some cleanup work to do tomorrow. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/855#comment:19> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5927: A type-level "implies" constraint on Constraints
by GHC 27 Feb '18

27 Feb '18

#5927: A type-level "implies" constraint on Constraints -------------------------------------+------------------------------------- Reporter: illissius | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 7.4.1 checker) | Keywords: Resolution: duplicate | QuantifiedConstraints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #2893 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Hm. That is not at all how I would have expected that instance to be solved. I agree that when typechecking `$dmshowsPrec`, we should start with: * `[W] Show (Exists c)` But don't we get that immediately? In other words, this typechecks: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE QuantifiedConstraints #-} {-# LANGUAGE UndecidableInstances #-} module T5927 where import Text.Show data Exists c where Exists :: c a => a -> Exists c instance Show (Exists c) where show = show showsPrec = undefined showList = undefined }}} Because when typechecking the RHS of `show`, we need `[W] Show (Exists c)`, but we already have that. It's only when we strengthen the context: {{{#!hs instance (forall a. c a => Show a) => Show (Exists c) where show = show showsPrec = undefined showList = undefined }}} That GHC complains: {{{ Bug.hs:12:10: error: • Could not deduce: c (Exists c) arising from a use of ‘show’ from the context: forall a. c a => Show a bound by the instance declaration at Bug.hs:11:10-53 • In the expression: show In an equation for ‘show’: show = show In the instance declaration for ‘Show (Exists c)’ • Relevant bindings include show :: Exists c -> String (bound at Bug.hs:12:3) | 12 | show = show | ^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5927#comment:34> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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